Effect of the ruby laser microbeam on mitochondria of KB cells supravitally stained by pinacyanol

With pinacyanol as the supravital stain, a preferential effect on mitochondria of KB cells was achieved by the irradiation with the ruby laser beam. The observation confirmed the results of other workers using janus green B in the same experimental system. The preferential effect on mitochondria was noted in the area extending 8-10 micro beyond the nonpreferential damage of 4-5 micro in diameter. The opaque material associated with mitochondria possibly represented coagulated protein. The effect involved cristae mitochondriales without severe disarrangement of their structure. The opaque material could be interpreted as the result of direct interaction between mitochondria and the laser beam, even though the mitochondria were noted outside of the previously estimated focal spot size of about 3 micro Within the thickness of 2-4 micro of monolayered cells, larger areas of damage can be accounted for by divergence of the beam which is focused by a microscope objective of very short focal length. A threshold of biologic effectiveness is probably also involved.

Fetal responses to acoustic stimuli

Prenatal tests of hearing are practically of great value in making an early diagnosis of deafness. Attempts were made to develop a relatively simple method of prenatal tests of hearing, and 134 fetuses of the 6th–10th month period of pregnancy were examined by means of this method. Pure tones of frequency 500, 1,000 and 2,000 Hz generated by a conventional audiometer were used as acoustic stimuli. Movements of the fetus as well as changes in the fetal pulse rate occurring during or immediately after the stimulation were used as criteria for the auditory response. One hundred and twenty-four of 134 fetuses responded to the stimulating tones, while the remaining 10 showed no responses. No responses were found in the fetuses in the 6th month of pregnancy.

Auditory responses in Tay-Sachs disease

It is demonstrated that local diagnosis of the hearing impairment and evaluating of the degenerating process in the central nervous system in Tay-Sachs disease may be possible by means of various kinds of audiometric methods applicable to young children, such as cerebral evoked response audiometry using a computer as well as startle response, auropalpebral reflex (APR) and cochleopupillary reflex (CPR) audiometries. Thresholds of startle response, APR, CPR during sleep and cerebral evoked potentials in response to sound stimuli were measured in three patients with Tay-Sachs disease. The thresholds of the startle response, APR and CPR were found to be comparable to those in normal newborn infants and normal young children, whereas no auditory cerebral evoked responses were detected by an average response computer even at the maximum intensity except for a case with the threshold of 80 dB. Since the startle response as well as APR and CPR may be integrated at the level of the brain stem and the cerebral evoked response may arise from the cerebral cortex over a wide area, it is suggested that the lack of the auditory cerebral evoked response probably reflects a predominant degeneration of the higher supranuclear auditory pathways.